Different types of transformers are being used in the area of energy supply. Besides the widely used transformers that are immersed in oil, there are also dry-type transformers. In dry-type transformers, a resin and the surrounding air have to assume the insulating and cooling functions of the oil. Since the oil fulfills these functions many times better, the performance ranges of the different transformer types are correspondingly different.
At the present time, large numbers of people are migrating to inner city areas to settle there. Accordingly, the energy supply has to be adapted to this development. Oil-filled transformers always involve the risk of a transformer fire, which would have devastating consequences in a densely populated area. A lively interest is therefore taken in the development of different dry-type transformers and the associated regulation devices.
A tapped transformer in which each phase consists of two windings is known from EP 0 213 461 B1. These windings each have two coupled-together sections with taps. A load selector, a so-called integrated on-load tap changer, is connected with the taps such that the load selector first connects the taps of the one winding and then those of the other winding. This applies likewise for disconnecting the taps. The switching from one tap to a next tap is performed in one step. The actual switching is carried out by a contact system with three contacts and two transition resistors. This embodiment has the following disadvantages:
First, all taps of the one winding part are switched on or off and afterward those of the other winding part. This results in an undesired magnetic imbalance of the transformer.
Loss of contact material due to commutation of the load current occurs at dissipation contacts and sliding contacts on moving across the middle position.
The switching step in switching across the middle position results in no change in voltage in the transformer.
The entire regulation range of the voltage of the transformer occasionally occurs between the step contacts and dissipation contacts. This means that large distances are required for high voltages.
The object of the invention is therefore to provide an on-load tap changer for voltage regulation that avoids the disadvantages of the prior art and can be used for higher voltages, a tapped transformer for voltage regulation that is safe and reliable, as well as a method of switching a tapped transformer for voltage regulation to ensure safe operation of the tapped transformer.
This object is attained according to a first aspect of the invention with an on-load tap changer for controlling voltage of a tapped transformer wherein
the tapped transformer has at least one phase to be regulated that has a first winding and a second winding;
the first winding has a regulating winding with even-numbered winding taps and a main winding, and the second winding has a regulating winding with odd-numbered winding taps and a main winding;
the first winding and the second winding having the regulating windings of the even-numbered and of the odd-numbered winding taps, are inductively coupled;
the on-load tap changer has a selector, in particular a first selector, for the alternating power-free preselection of the even-numbered or odd-numbered winding taps to be switched.
The on-load tap changer proposed according to the first aspect of the invention serves for controlling voltage of a tapped transformer. The tapped transformer has at least one phase to be regulated that has a first winding and a second winding. The first winding in each case has a regulating winding with even-numbered winding taps, and the second winding has a regulating winding with odd-numbered winding taps. One main winding is moreover provided, wherein the first winding and the second winding having the regulating windings of the even-numbered and of the odd-numbered winding taps, are inductively coupled. The on-load tap changer has a selector, in particular a first selector constructed such that an alternating power-free preselection of the even-numbered or odd-numbered winding taps to be switched is possible.
It can be provided that
the selector has a first selector part for the regulating winding with the even-numbered winding taps and a second selector part for the regulating winding with the odd-numbered winding taps for the power-free preselection of the winding taps to be switched.
It can be provided that each of the proposed on-load tap changers comprises
a load-diverter switch, in particular a first load-diverter switch, for carrying out the switching between the even-numbered or the odd-numbered winding taps of the regulating windings preselected load-free by the selector.
The selector has a first selector part for the regulating winding with the even-numbered winding taps and a second selector part for the regulating winding with the odd-numbered winding taps for the power-free preselection of the winding taps to be switched. For carrying out the switching, a load-diverter switch, in particular a first load-diverter switch, is provided between the even-numbered or the odd-numbered winding taps, and the load-diverter switch switches over between the regulating windings preselected load-free by the selector.
It can be provided that
the first selector part and the second selector part each have two selector arms for the winding taps of a regulating winding.
It can be provided that
the first selector part is electrically conductively connected with the even-numbered winding taps of the regulating winding of the first winding via step contacts;
the second selector part is electrically conductively connected with the odd-numbered winding taps of the regulating winding of the second winding via step contacts.
It can be provided that
each selector arm is electrically conductively connected with a respective dissipation rail and with a respective step contact of the corresponding regulating winding;
each dissipation rail is electrically conductively connected with the load-diverter switch.
It can be provided that
each selector arm is assigned a spindle, a belt, or a chain for linear movement.
The first selector part has two respective selector arms, and the second selector part has two respective selector arms formed for the winding taps of a regulating winding. The first selector part is electrically conductively connected with the even-numbered winding taps of the regulating winding of the first winding via step contacts. The second selector part is electrically conductively connected with the odd-numbered winding taps of the regulating winding of the second winding via step contacts. Each selector arm of the first or the second selector part is electrically conductively connected with a respective dissipation rail and with a respective step contact of the corresponding regulating winding. Each dissipation rail is electrically conductively connected with the load-diverter switch. Each selector arm is assigned a spindle, a belt, or a chain for linear movement.
It can be provided that
the load-diverter switch has a first switching side and a second switching side;
the first switching side disconnects or connects the first dissipation rail of the first selector part and the second dissipation rail of the second selector part;
the second switching side disconnects or connects the second dissipation rail of the first selector part and the first dissipation rail of the second selector part.
The load-diverter switch has a first switching side and a second switching side, with the first switching side disconnecting or connecting the first dissipation rail of the first selector part and the second dissipation rail of the second selector part. Likewise, the second switching side disconnects or connects the second dissipation rail of the first selector part and the first dissipation rail of the second selector part.
In one embodiment of the on-load tap changer, each switching side has at least one mechanical switch, two vacuum switching tubes and one resistor. The mechanical switch is connected in series with a first switching branch with a vacuum switching tube and with a parallel second switching branch with a vacuum switching tube and a resistor connected in series therewith.
In a further embodiment of the on-load tap changer, each switching side has at least one mechanical switch, two vacuum switching tubes and one resistor. A first switching branch is connected in parallel to a second switching branch, with the first switching branch having a mechanical switch and a vacuum switching tube connected in series and the second switching branch having a mechanical switch, a vacuum switching tube, and a resistor connected in series.
In a further embodiment of the on-load tap changer, each switching side has at least one mechanical switch, two vacuum switching tubes and one resistor. The mechanical switch is connected in series with a vacuum switching tube and is connected in series with a first switching branch with a resistor and with a second switching branch with a vacuum switching tube, with the first and the second switching branch being connected in parallel.
It can be provided that
each switching side has a permanent main contact connected in parallel to the first and the second switching branch.
It can be provided that
each switching side has a permanent main contact that directly conductively disconnects from each other or conductively connects with each other the first and the second dissipation rail.
Each switching side has a permanent main contact connected in parallel to the first and second switching branch. Furthermore, each switching side has a permanent main contact that directly conductively connects the first and the second dissipation rail with each other.
Each switching side can be formed in any manner as required and can comprise, for instance, at least one additional or further mechanical switch and/or at least one additional or further vacuum switching tube and/or at least one additional or further resistor and/or at least one additional or further permanent main contact.
It can be provided that each of the proposed on-load tap changers comprises
a motor drive, in particular a first motor drive coupled to the selector and/or to the load-diverter switch.
It can be provided that each of the proposed on-load tap changers comprises
a driven shaft, in particular a first driven shaft that couples the motor drive to the selector and/or to the load-diverter switch; and/or
a transmission, in particular a first transmission that couples the motor drive to the driven shaft or to the selector and/or to the load-diverter switch; and/or
a drive shaft, in particular a first drive shaft that couples the motor drive to the transmission.
The coupling of the first motor drive to the first selector and/or to the first load-diverter switch can be performed in any manner as required, for instance directly or indirectly, in particular via the driven shaft and/or the transmission and/or the drive shaft. In direct coupling, the first motor drive is preferably arranged as close as possible to the first selector and/or to the first load-diverter switch and/or fixed to the first selector and/or to the first load-diverter switch.
Preferentially, each shaft can be electrically insulating.
It can be provided that each of the proposed on-load tap changers comprises
an electrically insulating post with an upper post end and a lower post end that can be or is fixed to a base at ground potential;
with
the selector being fixed to the upper post end and arranged above the upper post end.
The post, which is also referred to as support, provides the insulation spacing required in the respective application instance, between the contacts, wires, and other parts of the on-load tap changer that are under voltage, and the ground potential. An insulation spacing of at least 72 kV or at least 123 kV or at least 145 kV can thus be achieved with sufficient height of the post.
The base can be, for instance, a part of the tapped transformer or of the on-load tap changer.
The on-load tap changer proposed according to the first aspect can be formed in any manner as required and can comprise, for instance, at least one additional or further selector and/or at least one additional or further load-diverter switch and/or at least one additional or further motor drive and/or at least one additional or further driven shaft and/or at least one additional or further transmission and/or at least one additional or further drive shaft and/or at least one additional or further post.
It can be provided that
the load-diverter switch is fixed to the upper post end and arranged above the upper post end, in particular below the selector; and/or
the transmission is fixed to the upper post end and arranged above the upper post end, in particular below the selector and/or above the resistors, or fixed to the lower post end and arranged below the lower post end, in particular in the base; and/or
the motor drive is fixed to the lower post end and arranged below the lower post end; and/or
the drive shaft or the driven shaft runs through the post from the lower post end to the upper post end.
It can be provided that
at least one of the resistors is a cast iron resistor.
In each switching process, the resistors are loaded with very high electrical power and heat up accordingly. They can cool off until the next switching process, but, according to the switching interval, this can be so short that they continue to increasingly heat up. If their temperature is too high, the switching interval has to be increased in order to provide more time for cooling off. This impairs the operation of the on-load tap changer. In comparison to wire resistors, such cast iron resistors have higher masses and thus heat up slower under the same energy input so that the switching interval has to be less frequently increased. This is significant in particular for dry-type transformers because their resistors are cooled with air, which is by far less effective than the cooling by means of the transformer oil, which is possible in oil transformers.
Preferably, the hot exhaust air accruing from the cooling of a dry-type transformer by means of air can be used as cooling air for the resistors, since this hot exhaust air is still cooler than the resistors under operation are.
It can be provided that each of the proposed on-load tap changers comprises
a second selector for a second phase to be regulated of the tapped transformer;
a third selector for a third phase to be regulated of the tapped transformer;
with
the second and the third selector being formed, in particular, like the first selector;
the second and the third phase being formed, in particular, like the first phase to be regulated;
the selectors being arranged at the corners of a triangle.
Such a three-phase on-load tap changer is suited, in particular, for a so-called temple-configuration transformer, in which the three phases are arranged symmetrically to each other at the corners of an equilateral triangle, and that is known from DE 40 29 097 A1, U.S. Pat. No. 5,202,664 A, EP 1 277 217 B1, EP 2 367 181 A1, and US 2013 328 652 A1, for instance. The three selectors can simply be assigned to the phases such that analog or similar or the same connection conditions exist for each phase-selector pair and, in particular, such that short connecting lines are possible. Instead of one such three-phase on-load tap changer, three one-phase on-load tap changers that are, in particular, formed according to the first aspect and/or identical in construction, can also be arranged symmetrically to each other at the corners of an equilateral triangle.
Preferably, the triangle is equilateral and the selectors at its corners are arranged symmetrically to each other.
It can be provided that each of the proposed on-load tap changers comprises
a second load-diverter switch assigned to the second selector;
a third load-diverter switch assigned to the third selector;
with
the second and the third load-diverter switch being formed, in particular, like the first load-diverter switch.
It can be provided that
the motor drive is coupled to the second and the third selector and/or to the second and the third load-diverter switch.
It can be provided that each of the proposed on-load tap changers comprises
a second driven shaft that couples the motor drive to the second selector and/or to the second load-diverter switch; and/or
a third driven shaft that couples the motor drive to the third selector and/or to the third load-diverter switch; and/or
a second transmission that couples the motor drive to the second driven shaft and to the second selector and/or to the second load-diverter switch; and/or
a third transmission that couples the motor drive to the third driven shaft and to the third selector and/or to the third load-diverter switch; and/or
a second drive shaft that couples the motor drive to the second transmission; and/or
a third drive shaft that couples the motor drive to the third transmission.
It can be provided that each of the proposed on-load tap changers comprises
a second motor drive coupled to the second selector and/or to the second load-diverter switch;
a third motor drive coupled to the third selector and/or to the third load-diverter switch;
with
the second and the third motor drive being formed, in particular, like the first motor drive; and/or
the couplings of the second and of the third motor drive to the respective selectors and/or load-diverter switches being performed, in particular, like the coupling of the first motor drive to the first selector and/or to the first load-diverter switch.
It can be provided that
the motor drives are synchronized, in particular, by mechanical and/or electronic coupling.
According to a second aspect, the invention proposes a tapped transformer for voltage regulation, which tapped transformer comprises an on-load tap changer, in particular a first on-load tap changer formed, in particular, according to the first aspect, and at least one phase to be regulated that has a first winding and a second winding, wherein
the first winding has a regulating winding with even-numbered winding taps and a main winding, and the second winding has a regulating winding with odd-numbered winding taps and a main winding;
the first winding and the second winding having the regulating windings of the even-numbered and of the odd-numbered winding taps, are inductively coupled;
the on-load tap changer has a first selector part and a second selector part for the alternating power-free preselection of the even-numbered or odd-numbered winding taps to be switched.
The tapped transformer for voltage regulation according to the second aspect of the invention comprises an on-load tap changer, in particular a first on-load tap changer formed, in particular, according to the first aspect, and at least one phase to be regulated that has a first winding and a second winding. The first winding has a regulating winding with even-numbered winding taps and a main winding. The second winding has a regulating winding with odd-numbered winding taps and a main winding. The first winding and the second winding having the regulating windings of the even-numbered and of the odd-numbered winding taps, are inductively coupled. The on-load tap changer has a first selector part and a second selector part for the alternating power-free preselection of the even-numbered or odd-numbered winding taps to be switched.
It can be provided that
the first selector part and the second selector part each have two selector arms for the winding taps of each one of the regulating windings;
with each selector arm of the first or the second selector part being electrically conductively connected with a respective dissipation rail and with a respective step contact of the corresponding regulating winding;
with each dissipation rail being electrically conductively connected with the on-load tap changer.
The first selector part and the second selector part each have two selector arms for the winding taps of each one of the regulating windings. Each selector arm of the first or the second selector part is electrically conductively connected with a respective dissipation rail with a respective step contact of the corresponding regulating winding. Each dissipation rail is electrically conductively connected with the on-load tap changer.
It can be provided that
a transmission, in particular a first transmission, is provided with a motor drive, in particular with a first motor drive, for activating the first selector part and the second selector part; and/or
each on-load tap changer of each one of the phases is connected with a common motor drive; and/or
the tapped transformer is a dry-type transformer.
A transmission, in particular a first transmission, is provided with a motor drive, in particular with a first motor drive, for effecting an activation of the first selector part and of the second selector part. Each on-load tap changer of each one of the phases is connected with a common motor drive. The tapped transformer is a dry-type transformer.
According to a first alternative, it can be provided that each of the proposed tapped transformers comprises
a second and a third phase to be regulated that are formed, in particular, like the first phase to be regulated;
with
the phases being arranged, in particular, symmetrically to each other at the corners of a first, in particular, equilateral triangle;
the on-load tap changer comprising a second selector for the second phase;
a third selector for the third phase;
the second and the third selector being formed, in particular, like the first selector;
the selectors being arranged at the corners of a second triangle.
Preferably, the second triangle is equilateral and the selectors at its corners are arranged symmetrically to each other. The symmetry axis of the second equilateral triangle is, in particular, coaxial to the symmetry axis of the first triangle.
According to a second alternative, it can be provided that each of the proposed tapped transformers comprises
a second and a third phase to be regulated that are formed, in particular, like the first phase to be regulated;
a second on-load tap changer for the second phase and a third on-load tap changer for the third phase, which on-load tap changers are formed, in particular, like the first on-load tap changer;
with
the phases being arranged, in particular, symmetrically to each other at the corners of a first, in particular, equilateral triangle;
the on-load tap changers being arranged at the corners of a second triangle.
Preferably, the second triangle is equilateral and the on-load tap changers at its corners are arranged symmetrically to each other. The symmetry axis of the second equilateral triangle is, in particular, coaxial to the symmetry axis of the first triangle.
These tapped transformers according to the two alternatives are thus temple-configuration transformers and are similar to the temple-configuration transformers known from DE 40 29 097 A1, U.S. Pat. No. 5,202,664 A, EP 1 277 217 B1, EP 2 367 181 A1, and US 2013 328 652 A1, for instance. In these tapped transformers, the three on-load tap changers or the three selectors can simply be assigned to the phases such that analog or similar or the same connection conditions exist for each phase-on-load tap changer pair and, in particular, such that short connecting lines are possible.
In both alternatives, it can be provided that the tapped transformer comprises
a motor drive for each phase, which motor drive is coupled to the respective selector and/or to the respective load-diverter switch;
with
the motor drives being arranged at the corners of a third triangle.
Preferably, the third triangle is equilateral and the motor drives at its corners are arranged symmetrically to each other. The symmetry axis of the third equilateral triangle is, in particular, coaxial to the symmetry axis of the first equilateral triangle and/or to the symmetry axis of the second equilateral triangle.
A method proposed according to the third aspect of the invention for switching a tapped transformer for voltage regulation, which tapped transformer is, in particular, formed according to the third aspect, comprises the following steps:
load-free preselection of an even-numbered or odd-numbered winding tap to be switched, of a regulating winding of a first or a second winding;
switching to the preselected even-numbered or odd-numbered winding tap of the first or second winding by means of one single load-diverter switch.
It can be provided that
the even-numbered or odd-numbered winding taps of a regulating winding of a first or a second winding are preselected and switched alternatingly.
The even-numbered or odd-numbered winding taps of a regulating winding of a first or a second winding are preselected and switched alternatingly.
The explanations and exemplifications regarding one of the aspects of the invention, in particular regarding individual features of this aspect, also apply correspondingly for the other aspects of the invention.